Optical fibers are used in an increasing number and variety of applications, such as a wide variety of telecommunications and data transmission applications. As a result, fiber optic networks must include an ever increasing number of enclosures in which one or more of the optical fibers are interconnected or otherwise terminated. For example, fiber optic networks, such as cable television (CATV) networks, may include a number of optical network units (ONUs) in which the optical signals propagating along the optical fibers are converted to respective electrical signals. In addition, telephone and CATV networks can include a number of network interface devices (NIDs); each NID is associated with a particular subscriber. Upon receiving the incoming optical signals, the NID splits and routes the signals to predetermined locations, such as to various telephone or CATV outlets. Like an ONU, the NID can also convert the incoming optical signals to electrical signals, if necessary. Fiber optic networks can also include a number of other closures, including splice closures, in which various ones of the optical fibers are spliced or optically connected. Regardless of the type, these enclosures provide protection, such as from moisture or other forms of environmental degradation, for the optical fibers and, more particularly, the point at which the optical fibers are spliced or are otherwise optically connected.
These enclosures, such as ONUs, NIDs, and other closures, typically include one or more receptacles in which the individual optical fibers of a fiber optic cable are connected to respective optical fibers within the enclosure. The optical fibers within the enclosure can then be interconnected or otherwise terminated as desired. Conventionally, receptacles have included a receptacle housing defining an internal cavity and an adapter sleeve disposed in a fixed position within the internal cavity defined by the receptacle housing. The adapter sleeve is designed to receive a pair of ferrules, each of which is mounted upon the end portions of a plurality of optical fibers. One of the ferrules is attached to the end of optical fibers extending from a cable, ribbon, or optical fiber device that extends into or is located in the interior of the enclosure to facilitate splicing or other interconnection or termination of the optical fibers. As described below, the other ferrule is mounted upon optical fibers extending from a cable, ribbon, or optical fiber device that extends outside or is located outside of the enclosure, such as the optical fibers of a fiber optic cable. The adapter sleeve assents in gross alignment of the ferrules, and ferrule guide pins or other alignment means assent in detailed alignment of the optical fibers mounted on the end faces of each ferrule.
In order to mate with the receptacle of a conventional enclosure, a fiber optic plug is mounted upon the end portion of a fiber optic cable. Typically, the plug includes a generally cylindrical plug body and a fiber optic connector including a plug ferrule disposed within the cylindrical plug body. In order to protect the plug ferrule, the cylindrical plug body may partially or completely surround the lateral sides of the fiber optic connector. While the end of the cylindrical plug body is open such that the ferrule is accessible, the end of the cylindrical plug body does extend slightly beyond the ferrule to provide further protection. The ferrule is mounted upon a plurality of optical fibers of the fiber optic cable such that mating of the plug and the receptacle will align or connect the optical fibers of the fiber optic cable with respective optical fibers within the enclosure.
In the process of mating the plug and the receptacle, the plug ferrule is inserted into one end of the adapter sleeve of the receptacle. The adapter sleeve therefore aligns the plug ferrule with a receptacle ferrule that is attached to the end portions of optical fibers from a cable, ribbon, or optical fiber device that extends into or is located in the interior of the enclosure. As a result of the construction of a conventional fiber optic plug, one end of the adapter sleeve is received within the open end of the plug body as the plug ferrule is inserted into the adapter sleeve. In addition, in order to retain the plug ferrule within the adapter sleeve, the fiber optic connector of the fiber optic plug and the adapter sleeve are designed to be mechanically coupled, such as by means of a pair of latches. While the latches effectively couple the plug ferrule and the adapter sleeve, the mechanical coupling of the fiber optic connector and the adapter sleeve disadvantageously limit float between the plug ferrule and the adapter sleeve.
Once the plug and the receptacle have been mated, the fiber optic cable may be subjected to forces that create torque upon the fiber optic connector including the plug ferrule. This torque will disadvantageously increase the attenuation of the optical signals transmitted via the optical fibers upon which the plug ferrule is mounted. Even worse, this torque may break the optical fiber. Traditionally, the fiber optic cables upon which the fiber optic plugs are mounted have been quite flexible such that the plug ferrule has been subjected to only minimal amounts of torque. More recently, however, fiber optic plugs are being installed upon fiber optic cables that are much stiffer, such as the armored fiber optic cables designed for outdoor applications. As a result of the increased stiffness of these fiber optic cables, forces upon the fiber optic cable are much more readily transmitted to the plug ferrule, thereby imposing increased torque upon the plug ferrule. As a result of the increased attenuation of the optical signals created by the torque, it would be advantageous for the fiber optic plug to at least partially isolate the plug ferrule and the optical fibers upon which the plug ferrule is mounted from those forces to which the fiber optic cable are subjected.
Prior to engagement with the receptacle, a fiber optic cable, including the end portion of the fiber optic cable upon which the plug is mounted, must oftentimes be installed, such as by pulling, along a predetermined cable path. In some instances, the fiber optic cable must extend through ducts or other small passageways that are not much larger than the fiber optic cable itself. Since the plug body must be sufficiently large to receive and surround one end of the adapter sleeve, the size of the plug body may limit the minimum size of the duct or other passageway through which the fiber optic cable is installed. This limitation on the minimum size of the duct is becoming increasingly disadvantageous as additional emphasis is now placed upon reducing the space required for installing a fiber optic cable, i.e., reducing the duct size, in view of the large number of fiber optic cables that are currently installed. To date, however, reductions in the size of the duct through which a fiber optic cable is pulled are limited, at least in part, by the size of the plug body mounted upon the end portion of the fiber optic cable.
In order to pull a fiber optic cable, a pulling grip is typically mounted to the leading end of the fiber optic cable including the fiber optic plug in those embodiments in which a fiber optic plug has been mounted upon the end portion of the fiber optic cable. The pulling grip is designed to securely engage the end of the fiber optic cable load coupled to the strength element of the cable and to provide a point of attachment for a rope, a cable or the like that is utilized to pull the fiber optic cable. Since the fiber optic cable must frequently be pulled along a predetermined cable path that twists and turns, pulling grips designs are adapted to swivel or rotate relative to the fiber optic cable to avoid imparting undesirable torque on the fiber optic cable as it is pulled along a path. Typically, a pulling grip that is adapted to swivel relative to the fiber optic cable includes a plurality of components that must be connected to the fiber optic cable. The components of this conventional pulling grip are connected to each other in a manner that permits the component to which the rope, cable, or the like is attached to rotate or swivel relative to the component directly attached to the fiber optic cable. Thus, while pulling grips that swivel relative to the fiber optic cable are available, it would be advantageous to provide a pulling grip that is adapted to swivel relative to the fiber optic cable that has a simpler construction in order to facilitate use of the pulling grip and to reduce the cost of the pulling grip.